SIMRAD GD10 IR GAS DETECTOR

1 SIMRAD GD10 IR GAS DETECTOR Operating Manual 5th Edition P3359E October 1999

1 CONTENTS Section Page 1. PRODUCT DESCRIPTION 3 1.1 General description 3 1.2 Construction 3 1.3 Application areas 4 1.4 Technical data 4 1.5 Certification 6 1.6 Certificates 6 2. TECHNICAL DESCRIPTION 7 2.1 Introduction 7 2.2 The GD10 concept 7 2.3 Performance characteristics 9 2.3.1 Gas data 9 2.3.2 Cross reference to other gases 10 2.4 Gas detection system 10 3. INSTALLATION 11 3.1 Mounting the GD10 11 3.1.1 Location 11 3.1.2 Ventilation duct or pipe mounting 11 3.1.3 Orientation 14 3.1.4 Mounting the GD10 14 3.1.4.1 Retrofit mounting 15 3.2 Electrical connection 15 3.2.1 Terminal compartment 15 3.2.2 Output cable connections 16 3.2.2.1 3-Wire output cable connections 16 3.2.2.2 Retrofit wiring 17 3.2.2.3 Recommended cable types 18 3.2.2.4 Initial wiring checks 18 4. OPERATION 19 4.1 Start-up procedure 19 5. MAINTENANCE 20 5.1 General 20 5.2 Failure indications 20 5.3 Cleaning of optical window and mirror 22 5.4 Functional test 22 5.5 Calibration test 23 6.0 ORDERING INFORMATION 24 6.1 Spare Parts List 25

2 Figures and Tables Fig. 1.1 GD10, outline dimensions 5 Fig. 2.1 Transmittance as a function of wavelength 7 Fig. 2.2 Block diagram, GD10 8 Fig. 3.1 Ventilation duct or pipe mounting. Duct Mounting Flange Kit for mounting in narrow ducts and pipes 12 Fig. 3.2 Exploded view, Duct Mounting Flange kit 13 Fig. 3.3 Ventilation duct or pipe mounting. GD10 mounted using the Duct Mounting Bracket for mounting in wide ducts or pipes 13 Fig. 3.4 Orientation of the GD10 in relation to flow direction 14 Fig. 3.5 GD10 mounted by means of projecting mounting leg 14 Fig. 3.6 Terminal compartment 15 Fig. 3.7 Bridge interface installation 17 Fig. 4.1 Signal output during start-up period 19 Fig. 5.1 Test procedure 21 Fig. 5.2 Set-up of functional test 22 Fig. 5.3 Set-up of calibration test 23

3 1. PRODUCT DESCRIPTION 1.1 General description The Simrad GD10 Gas Detector is a point detector for gas concentration monitoring in potentially hazardous and/or poisonous environments. The GD10 is based on infrared absorption and uses the latest developments in analogue and microprocessor technology. Solid state design improves reliability, long-term stability and accuracy in continuous measurement of gas concentration in ambient air. Compared with catalytic sensors, the GD10 has the following advantages: Presence of oxygen is not required for correct measurement, which makes the GD10 suitable even in an inert gas atmosphere. There is no possibility of poisoning of the detector since no chemical reaction occurs, i.e. silicon vapours and H 2 S have no effect on the detector or the measurement. The gas flow rate has no influence on accuracy. There are no saturation effects which could lead to false measurements. Thus, the detector is capable of measuring gas concentrations up to 100% vol. The detector has a continuous self-test function, and reports faults to the central system. Total system costs can be dramatically reduced with the GD10 : High reliability results in low test frequency and no calibration costs. Voting systems to increase reliability are not required, which reduces the number of detectors up to 66 %. 1.2 Construction A complete GD10 Gas Detector consists of the following: An external gas measuring path where gas is measured by means of IR radiation. A weather protection enclosure is mounted around the measuring path to protect the optical surfaces from rain and dust. An optoelectronic unit, which generates IR radiation to the gas measuring path, measures the reflected IR radiation from the gas measuring path and calculates the gas concentration. This unit is enclosed by an EExd certified housing. A terminal compartment with cable entry and mini-terminals for electrical connection. The compartment is protected by a cover and is EExe certified.

4 1.3 Application areas The GD10 is designed for detection of hydrocarbon gases in hazardous areas on offshore platforms and petrochemical plants, but it can also be used in a variety of other applications. For retrofit applications, a bridge interface is available allowing the detector to be connected directly to catalytic systems, using the existing cabling and control modules. With the Sample Flow Housing mounted, the detector can be used in aspirator systems. The GD10 is housed in a compact stainless steel enclosure, which is certified flame-proof, meeting the requirements of EN 50018. 1.4 Technical data (0-100% LEL methane, 5 sec. response time) Specification for other types on request Detection range 0-100% LEL (0-5% Vol.) methane - option 0-100% Vol. methane - option Other gases on request Long-term stability Better than ±5% of full scale reading Accuracy, standard 5 sec. Better than ±3% of full scale between 0-50 % reading Better than ±5% of full scale between 50-100 % reading Response time, standard 5 sec. T50 = 2.5 sec. T90 = 6 sec. Response time, option 1 sec. T50 = 1 sec. T90 = 2 sec. Start-up time <60 sec. Self-test Continuous Calibration Factory set Sensor warnings: - Early clean optics Dirt accumulation on windows (gas measurements interrupted by following signal: 1 ma for 3 sec. at 5 min. intervals) - Clean optics Dirt accumulation on windows (1 ma output signal) - Sensor failure Internal malfunction in the sensor (0 ma output signal) Output signal: - Standard Current source 4-20 ma, max. load impedance 500 Ω - Option Current sink 4-20 ma Electrical: - Power supply 18-32 V DC - Power consumption Approx. 3.5 W - Start-up current 0.3 A for 0.3 sec. - Electrical connection 3 wires (M20 EExe cable gland)

5 Temperature range: - Storage -40 C to +70 C - Operating -20 C to +45 C - Operating (option) -40 C to +60 C - Humidity (operation) 99% RH non-condensing Explosion-proof housing: - Main compartment EExd IIC T6 - Terminal compartment EExe Protection category IP66/IP67 DIN 40050 Housing material Stainless steel SIS2343 (ASTM 316) Weight, incl. Weather Protection Approx. 2.9 kg Accessories Weather Protection Sample Flow Housing Duct Mounting Brackets Figure 1.1 GD10, outline dimensions (mm)

6 1.5 Certification The GD10 has been certified according to the requirements for "Electrical apparatus for explosive atmospheres" given by CENELEC in the following standards: EN 50014 (1977) EN 50018 (1977) EN 50019 (1977) EN 50054 (1991) Electrical apparatus for potentially explosive atmospheres. General requirements Amendment No. 1 (July 1979) Amendment No. 2 (June 1982) Amendment No. 3 (December 1982) Amendment No. 4 (December 1982) Amendment No. 5 (February 1986) Electrical apparatus for potentially explosive atmospheres. Flame-proof enclosure d Amendment No. 1 (July 1979) Amendment No. 2 (December 1982) Amendment No. 3 (November 1985) Electrical apparatus for potentially explosive atmospheres. Increased safety e Amendment No. 1 (July 1979) Amendment No. 2 (September 1983) Amendment No. 3 (December 1985) Electrical apparatus for the detection and measurement of combustible gases. General requirements and test methods EN 50057 Performance requirements for Group II apparatus indicating up to 100 % lower explosive limit EN 50081-1 EN 50082-2 Electromagnetic compatibility - Generic emission standard Part 1: Residential, commercial and light industry Electromagnetic compatibility - Generic immunity standard Part 2: Industrial environment 1.6 Certificates SAA Certification (SIMTARS) AUS Ex 2393 Exd e II C T6 (Tamb 20C to + 60C) IP66/67 Epsilon x Certificate of Conformity: NEMKO No. Ex96D321 SIRA Certificate of Conformity No.: Ex 97Y8025

7 2. TECHNICAL DESCRIPTION 2.1 Introduction The GD10 Gas Detector from Simrad Optronics is a point detector for use in hazardous areas. A high stability infrared radiation source combined with the latest developments in optical and electronic design have led to the realisation of a compact, accurate and cost-effective instrument able to monitor explosion dangers in real-world environments. 2.2 The GD10 concept The concept is based on measurement of infrared radiation passing through a volume of gas. The GD10 employs a dual beam, dual wavelength measuring principle with separate optical detectors for maximum stability and reliability. Since different types of gas have unique absorption spectra, they can easily be identified by proper selection of an infrared wavelength at which absorption is measured. Radiation at another wavelength measures the overall transmission through the optical system and the air volume. By comparing the transmission at the two wavelengths, the gas concentration in the air is determined. Having chosen a wavelength which is characteristic of one type of gas, other types of gas will not cause false alarms. Using a solid-state IR source instead of a lamp ensures high reliability and long-term stability with no regular maintenance required during equipment lifetime. Figure 2.1 Transmittance as a function of wavelength

8 Refer to Figure 2.2 below. Radiation from two infrared sources passes through two narrowband filters selecting a measuring wavelength and a reference wavelength. The sources are electronically chopped. Radiation is divided by a beamsplitter into an internal and external path. The internal path is viewed by the compensation detector, and the external path is viewed by the measuring (main) detector. The compensation detector monitors and compensates for drift in sources or detectors. The main detector monitors the external measuring path and detects whether the selected gas is present. The four signals, two from the compensation detector and two from the main detector, are amplified, digitised and fed to the microprocessor. The signals are used by the microprocessor to calculate the gas concentration. The gas response is then linearized and presented as either a voltage, a current or a digital output signal. Internal signals are compared with test limits to monitor electronics and optical parts. If values outside the test limits are found, specific error messages are given. Optical filter characteristics remain constant over time, and drift in the other components is monitored and compensated by the dual wavelength, dual path concept. This means that the zero and gas span factory calibration will remain stable regardless of component drift, and that the detector needs no manual recalibration after factory calibration. Figure 2.2 Block diagram, GD10

9 2.3 Performance characteristics 2.3.1 Gas data The GD10 standard version is factory calibrated and linearized with methane gas in the 0-100 % LEL range. Calibration/linearization to other gases or concentrations can also be done. Accurate measurements can only be achieved by having the detector calibrated for the gas it is intended to measure. Gases such as ethane, propane and butane are also detected by the GD10. A GD10 calibrated for methane has a higher sensitivity to these gases than to methane. This means that explosion danger from other HC-gases will always be detected by the GD10. Because of tolerances in the infrared filters, readings of other gases than methane will not be exact when the detector is calibrated to 100% LEL methane. Converting % LEL to % v/v is based on ISO10156, Second edition 1996-02-15: Gases and gas mixtures - Determination of fire potential and oxidizing ability for the selection of cylinder valve outlets. The GD10 is designed for normal atmosphere pressure variation, but it is certified for pressure limits from 86 to 108 kpa.

10 2.3.2 Cross interference to other gases Hydrocarbon gases such as methane, ethane, propane and butane are absorbing at a signal wavelength of 3.3 µm. These gases do not interfere at the reference wavelength at 3.0 µm. If the atmosphere to be monitored contains gases such as acetylene that absorb at the reference wavelength of 3.0 µm, misleading measurements may be obtained depending on the interfering gas concentration. In such cases, contact Simrad Optronics for information. A modified GD10 using another reference wavelength will eliminate the problems. Water vapour, carbon dioxide, oxygen, nitrogen and other gases, which are present in normal air will not influence the measurements. 2.4 Gas detection system Since the GD10 is a point detector, it must be mounted where gas leakage is most likely to occur. It should be considered whether the gas in question is heavier or lighter than air. The number of sensors recommended depends on room size, shape, airflow and so on. The GD10 can also be mounted on an air duct wall. For this purpose, duct mounting kits are available. Owing to high reliability and extensive self-testing, the GD10 dramatically reduces the number of sensors needed, and voting between sensors is no longer necessary. As a result, maintenance routines can be relaxed without loosing system confidence and repair work is reduced to a minimum. For detailed mounting descriptions, see section 3.1

11 3. INSTALLATION 3.1 Mounting the GD10 3.1.1 Location The location of each detector should preferably be determined at the system design stage. NOTE: The area in which the detector may be mounted must be in accordance with the certification of the detector and in accordance with the standards of the appropriate authority in the country concerned. Choice of mounting area: The detector should be mounted where gas leakage is most likely to occur. To detect methane, which is lighter than air, inside an enclosed area the detector should be mounted high in the area to be protected or immediately above potential leakage sites. To detect gases heavier than air, e.g. propane, the detector should be mounted below the potential leakage site. The detector should be mounted in a place where maintenance, i.e. cleaning of the optics, is easily performed. The detector may be mounted in areas where no oxygen is present. The detector may be mounted in areas with strong airflow The detector should NOT be mounted where it could be exposed to water drenching. NOTE: The detector must always be used with the Weather Protection or Sample Flow Housing mounted. Exception to this must be discussed with Simrad Optronics. 3.1.2 Ventilation duct or pipe mounting If installed in a ventilation duct or pipe, the mounting arrangement and accessories shown in Figure 3.1 and 3.2 should be used. The Duct Mounting Bracket shown in Fig. 3.2 allows the GD10 to be positioned in the core of the airflow in wide ducts or pipes. NOTE: Avoid direct light on lens and mirror if the GD10 is mounted without the Weather Protection.

12 In order to achieve minimum response time, the Weather Protection must be oriented with the flow direction indicator facing away from the air flow. See procedure in section 3.1.3. The sensor must be mounted in straight parts of the duct where air flow is laminar. Avoid mounting the sensor in duct bends and places where the air flow is turbulent. Flange 599-811939.8 Duct wall Flow direction indicator Duct Mounting Flange Kit GD10: 499-811938.0 GD10C: 499-811187.4 >126 mm Gasket Not included in kit Figure 3.1 Ventilation duct or pipe mounting. Duct Mounting Flange Kit for mounting in narrow ducts and pipes.

13 Figure 3.2 Exploded view, Duct Mount Flange Kit Figure 3.3 Ventilation duct or pipe mounting. GD10 mounted using the Duct Mounting Bracket for mounting in wide ducts or pipes

14 3.1.3 Orientation The detector should be mounted so that the longitudinal axis of the detector is horizontal. This will prevent accumulation of water and dust on the optics. The Weather Protection must always be oriented correctly for optimal performance. NOTE: When the GD10 is mounted outdoors, the flow direction indicator must point upwards. See Flow Direction Indicator in Fig. 3.3 below. Orientation of the Weather Protection is performed as follows: Use a screwdriver to loosen the two screws on the Weather Protection Rotate the Weather Protection to correct position Tighten the screw with a torque of max. 0.5 Nm Flow direction indicator Flow direction Fig. 3.4 Orientation of GD10 in relation to flow direction 3.1.4 Mounting the GD10 The detector is mounted by means of a projecting mounting leg using two M8 screws and washers, or by means of the Duct Mounting Flange Kit (4 x M8 screws). Weather Protection M8 screw Fig. 3.5 GD10 mounted by means of mounting leg

15 3.1.4.1 Retrofit mounting For retrofit of catalytic sensors an adapter plate is available allowing the GD10 to be mounted using the same hole pattern as most catalytic sensors. Refer to section 6.0. 3.2 Electrical connections 3.2.1 Terminal compartment The terminal compartment is accessible by removing the circular terminal cover. (Loosen the four M5 screws.) Refer to Figure 3.5. The terminal compartment, including the 5 mini-terminals for electrical connection, is shown in Figure 3.5 below. The installation wiring enters the terminal compartment via a single M20 EExe cable gland, which can be mounted on either side of the compartment. The unused entry is blanked with an EExe cover. Figure 3.6 Terminal compartment Terminal 1 +24 V DC Terminal 2 24 V return (0 V) Terminal 3 4-20 ma output Terminal 4 Not used Terminal 5 Not used

16 3.2.2 Output cable connections The detector has two output modes: - Current source 4-20 ma (standard) - Current sink 4-20 ma (option) The mode is factory set. 3.2.2.1 3-wire output cable connection The cable connections are as follows: Terminal No l: +24V DC Terminal No 2: 0 V DC (24 V and signal return) Terminal No 3: Signal output The shield of the cable should be connected to instrument earth in the central control module.

17 3.2.2.2 Retrofit wiring The GD10 Gas Detector has been designed to be fully interchangeable with existing catalytic sensors, using the same 3-wire cable and the same bridge input control modules. This application requires the Bridge Interface to be employed as shown in Figure 3.7 below. The Bridge Interface (Simrad reg. no. 109-804511.4) converts the standard 4-20 ma active current output from the GD10 to a bridge signal input, which is a typical standard for several control modules in use today. The Bridge Interface operates on a standard 24V DC supply. The complete Bridge Interface assembly is contained in a plastic housing, which clips onto a standard DIN mounting rail. This allows several channels to be interfaced in a space-saving way. NOTE: As signal levels, polarity, loading, stability and fault testing differ between manufacturers of catalytic modules, Simrad Optronics must be contacted for correct setting of variables in the Bridge Interface. Figure 3.7 Bridge interface installation

18 3.2.2.3 Recommended cable types The cable selected for interfacing the control equipment should be approved for use in the actual area. It is recommended to use shielded cables. Cables should be of a fine multi-strand type with a cross-section between 0.5 mm 2 and 1.5 mm 2. The cable enters the terminal compartment via an EExe cable gland. Several options of gland fittings are available. 3.2.2.4 Initial wiring checks After wiring as detailed above, and before applying power, ensure that: +24V DC is connected to terminal l 0 V DC is connected to terminal 2 Signal output is connected to terminal 3

19 4. OPERATION 4.1 Start-up procedure Ensure that system wiring and control system are in working order before switching on power to the detector. The detector will then perform self-test and internal signal adjustments lasting for approx. 60 seconds and switch to measuring mode. The output signal from the detector during this period is shown in Figure 4.1 below (current output of the GD10 standard version). Signal output before 60 seconds is 0 ma, and signal output after 60 seconds is 4 ma (if no gas is present). Figure 4.l Signal output during start-up period

20 5. MAINTENANCE NOTE: The GD10 has no user adjustable parts. It is not recommended to open the GD10, as this will change the internal atmosphere, and the initial calibration could be affected. 5.1 General The GD10 has been designed to require a minimum of maintenance. The only necessary maintenance is to inspect visually that the Weather Protection is not clogged in heavily contaminated areas. 5.2 Failure indications The internal microprocessor performs continuous self-testing of optical and electronic functions. If a fatal error should occur in the electronics or optics, the processor will generate a 0 ma output signal, indicating sensor failure. The detector should then be checked according to Figure 5.1 on the next page. Do not return the instrument to Simrad Optronics for repair if this test has not been performed.

21 NOTE: Avoid direct light on lens and mirror if testing without the Weather Protection. NOTE: Ensure that no gas is present in the measuring chamber when testing. Figure 5.1 Test procedure

22 5.3 Cleaning of optical window and mirror If the optical window and mirror have to be cleaned, use a soft and clean tissue to rub off the contamination. The window and mirror are made of sapphire, which is highly resistant to rubbing. Make sure that the whole optical surface is clean. NOTE: For difficult contaminants the mirror and lens can be cleaned with an equal-part mixture of isopropyl alcohol and water. Do not perform any testing of the sensor before cleaning solution is dried away. 5.4 Functional test In order to perform functional test of the detector a test gas can be applied through a 6 mm test nozzle on the front of the Weather Protection housing. Read the effect on the sensor output signal or through the gas detection system. The GD10 has been designed for long-term stability, and in order to retain the high reliability of the GD10 it is only necessary to monitor the detector's zero point and error messages from the detector. To avoid inhibiting the response time of the detector, the Weather Protection has been designed as open as possible to facilitate gas flow-through. Therefore, it is difficult to fill the gas measuring path completely with test gas, especially in windy weather. Functional test of the GD10 can be performed as follows: If there is no air movement, a test gas flow of minimum 4 litres/minute will give approximately the same value as the test gas. If there is an air movement of 0.5 m/sec., the test gas flow must be increased to 20 litres/minute to show the same value. At high air velocities, when it is difficult to obtain sufficient output using test gas in the LEL area, a test gas in the 50-100% vol. range can be employed. This gas can be applied at high flow for 2-5 seconds to acquire a concentration of test gas in the gas measuring path for a short period. Figure 5.2 Set-up of functional test

23 5.5 Calibration test Remove the Weather Protection and replace it with the Sample Flow Housing. In order to perform calibration test, use a calibrated gas and apply it to the Sample Flow Housing (reg. no. 499-810874.8). Ensure that optical surfaces are clean before mounting the Sample Flow Housing. Apply a certified test gas of approx. 50 % of full scale methane as shown in Fig. 5.3 below. Gas flow should be approx. 1 litres/minute., wait approx. 2 min. to ensure that the Sample Flow Housing is completely filled with gas. Read sensor output or read output through the gas detection system. NOTE: Use the same type of gas as the detector has been calibrated for. Figure 5.3 Set-up of calibration test

24 6. ORDERING INFORMATION Description Order number GD10P 0-100 % LEL 128-810867.2 Methane 5 sec. source Other standard and special versions available on request Weather Protection Kit GD10P 499-810913.4 Housing Sample Flow Assy 499-810874.8 Bridge Interface Assy 109-804511.4 Duct Mounting Bracket 599-811086.8 Duct Mounting Flange Kit GD10 499-811938.0 1: Plate Adapter (junction box/gd10) 499-811176.7 2: Plate Adapter (GD100/GD10) 599-811547.9 1 2

25 6.1 Spare Parts List Designation Simrad Part Number Weather Protection Kit GD10P 499-810913.4 Cap, Slip-on 599-904176.5 Cover Assy 499-810869.8 If you require assistance or need additional information please contact: Gastech Australia Ph: 61 8 9242 1869 Fax: 61 8 9242 1959 Email: Website: info@gastech.com.au www.gastech.com.au